/*
 * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
 * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
 * copyright and warranty notices given in that book:
 *
 * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
 *
 *
 * "The authors and publisher have taken care in the preparation of this book,
 * but make no expressed or implied warranty of any kind and assume no
 * responsibility for errors or omissions. No liability is assumed for
 * incidental or consequential damages in connection with or arising out of the
 * use of the information or programs contained herein."
 *
 * Permission is granted for this code to be used for educational purposes in
 * association with the book, given proper citation if and when posted or
 * reproduced.Any commercial use of this code requires the explicit written
 * permission of the publisher, Addison-Wesley Professional, a division of
 * Pearson Education, Inc. Send your request for permission, stating clearly
 * what code you would like to use, and in what specific way, to the following
 * address:
 *
 *  Pearson Education, Inc.
 *  Rights and Contracts Department
 *  75 Arlington Street, Suite 300
 *  Boston, MA 02216
 *  Fax: (617) 848-7047
*/

#include <stdexcept>

template <class T> class Handle
{
public:
	// unbound handle
	Handle(T* p = 0): ptr(p), use(new size_t(1)) { }

	// overloaded operators to support pointer behavior
	T& operator*();
	T* operator->();
	const T& operator*() const;
	const T* operator->() const;

	// copy control: normal pointer behavior, but last Handle deletes the object
	Handle(const Handle& h): ptr(h.ptr), use(h.use)
	{
		++*use;
	}
	Handle& operator=(const Handle&);
	~Handle()
	{
		rem_ref();
	}
private:
	T* ptr;          // shared object
	size_t* use;     // count of how many Handles point to *ptr
	void rem_ref()
	{
		if (--*use == 0) {
			delete ptr;
			delete use;
		}
	}
};

template <class T>
inline Handle<T>& Handle<T>::operator=(const Handle& rhs)
{
	++*rhs.use;    // protect against self-assignment
	rem_ref();     // decrement use count and delete pointers if needed
	ptr = rhs.ptr;
	use = rhs.use;
	return *this;
}

template <class T> inline T& Handle<T>::operator*()
{
	if (ptr) return *ptr;
	throw std::runtime_error
	("dereference of unbound Handle");
}
template <class T> inline T* Handle<T>::operator->()
{
	if (ptr) return ptr;
	throw std::runtime_error
	("access through unbound Handle");

}

template <class T> inline
const T& Handle<T>::operator*() const
{
	if (ptr) return *ptr;
	throw std::runtime_error("dereference of unbound Handle");
}
template <class T> inline
const T* Handle<T>::operator->() const
{
	if (ptr) return ptr;
	throw std::runtime_error("access through unbound Handle");

}
